|
Problem IC68993
|
Status: Closed |
PERFORMANCE ISSUE WHEN CAST AROUND LITERAL FOR BIT DATA IS PRESENT |
| product: |
DB2 FOR LUW / DB2FORLUW / 980 - DB2 |
| Problem description: |
This problem happens ONLY WHEN CAST for BIT DATA and only when
it is on one side and not another and only when literals.
DB2 generate non-optimal plans because BIT_STRING function is
injected and it prevents certain optimization logic. Please
consider the following examples:
CAST(x'00' AS CHAR(1) FOR BIT DATA) = CAST(x'01' AS CHAR(1) FOR
BIT DATA)
- will perform well
x'00' = x'01'
- will perform well
CAST(x'00' AS CHAR(1) FOR BIT DATA) = x'01'
- here PERFROMANCE is BAD. |
| Problem Summary: |
****************************************************************
* USERS AFFECTED: *
* All *
****************************************************************
* PROBLEM DESCRIPTION: *
* This problem happens ONLY WHEN CAST for BIT DATA and only *
* when *
* it is on one side and not another and only when literals. *
* *
* DB2 generate non-optimal plans because BIT_STRING function *
* is *
* injected and it prevents certain optimization logic. Please *
* *
* consider the following examples: *
* *
* *
* *
* CAST(x'00' AS CHAR(1) FOR BIT DATA) = CAST(x'01' AS CHAR(1) *
* FOR *
* BIT DATA) *
* *
* - will perform well *
* *
* *
* *
* x'00' = x'01' *
* *
* - will perform well *
* *
* *
* *
* CAST(x'00' AS CHAR(1) FOR BIT DATA) = x'01' *
* *
* - here PERFROMANCE is BAD. *
****************************************************************
* RECOMMENDATION: *
* Upgrade to DB2 V9.8 FP4 *
**************************************************************** |
| Local Fix: |
rewrite the statement in the following manner
CAST(x'00' AS CHAR(1) FOR BIT DATA) = CAST(x'01' AS CHAR(1) FOR
BIT DATA) |
| available fix packs: |
DB2 Version 9.8 Fix Pack 4 for AIX and Linux
DB2 Version 9.8 Fix Pack 5 for AIX and Linux
|
| Solution |
First fixed in DB2 v 9.8 Fixpack 4 |
| Workaround |
not known / see Local fix |
| Timestamps |
Date - problem reported :
Date - problem closed :
Date - last modified :
| 07.06.2010
01.08.2011
01.08.2011 |
| Problem solved at the following versions (IBM BugInfos) |
9.8.FP4
|
| Problem solved according to the fixlist(s) of the following version(s) |
| 9.8.0.4
|
 |
